The Paddington International Virtual Chromoendoscopy Score in ulcerative colitis exhibits very good inter-rater agreement after computerized module training: a multicentre study across academic and community practice (with video)

Research output: Contribution to journalArticlepeer-review


External organisations

  • Department of Medicine, Division of Gastroenterology, HSK Hospital
  • University of Calgary
  • Department of Gastroenterology, Royal Wolverhampton Hospitals NHS Trust
  • University Hospital Birmingham
  • University Hospitals Coventry and Warwickshire NHS Trust
  • University Hospitals Leuven


Introduction: Electronic virtual chromoendoscopy (EVC) can demonstrate ongoing disease activity in ulcerative colitis (UC) even when Mayo subscores suggest healing. However, applicability of EVC technology outside the expert setting has yet to be determined.

Methods: 15 participants across five centres reviewed a computerised training module outlining high definition (HD) and EVC (i-Scan) colonoscopy modes. Inter-observer agreement was then tested (Mayo score, UCEIS and the Paddington International virtual ChromoendoScopy ScOre [PICaSSO] for UC), using a colonoscopy video library (n=30 cases reviewed pre- and n=30 post-training). Knowledge sustainability was re-tested in a second round (n=42 cases; 9/15 participants), 6 months post-training provision.

Results: Pre-training intraclass correlation coefficients (ICC) were good for the Mayo endoscopic subscore (ICC:0.775), UCEIS scoring erosions/ulcers (ICC:0.770) and UCEIS overall (ICC:0.786), and for mucosal (ICC:0.754) and vascular components of PICaSSO (ICC:0.622). For the vascular components of UCEIS, agreement was only moderate (ICC:0.429), and did not enhance post-training (ICC:0.417); unlike for PICaSSO which improved (mucosal ICC:0.848; vascular: 0.746). Histological correlation using the New York Mt. Sinai System was strong for both PICaSSO components (Spearman’s rho for mucosal: 0.925, and vascular: 0.873; p<0.001 for both). Moreover, accuracy in specifically discriminating quiescent from mild histological strata was strongest for PICaSSO (AUROC for mucosal: 0.781; vascular: 0.715), compared to Mayo (AUROC:0.708) and UCEIS (AUROC for UCEIS overall: 0.705; vascular: 0.562; bleeding: 0.645; erosions/ulcers: 0.696). Inter-rater reliability for PICaSSO was sustained by round two participants (Round 1 and 2 ICC for mucosal: 0.873 and 0.869,respectively; and vascular: 0.715 and 0.783, respectively), together with histological correlation (rho mucosal: 0.934, vascular: 0.938; p<0.001 for both).

Conclusion: PICaSSO demonstrates good inter-observer agreement across all levels of experience, providing excellent correlation with histology. Given ability to discriminate subtle endoscopic features, PICaSSO may be applied to refine stratified treatment paradigms for UC patients.


Original languageEnglish
Pages (from-to)95-106.e2
JournalGastrointestinal Endoscopy
Issue number1
Early online date13 Mar 2018
Publication statusPublished - Jul 2018


  • colonoscopy , endoscopic remission , histological remission , inflammatory bowel disease, mucosal healing , risk stratification